A. Field of the Invention
The present invention relates to a liquid colored toner composition suitable for use in contact and gap electrostatic transfer processes. The present invention further relates to a liquid colored toner composition which comprises a mixture of (1) a colored predispersion which is made by mixing together at least one selected nonpolymeric resin material, at least one selected polymeric plasticizer, and at least one selected colorant material, (2) a carrier liquid, and (3) a charge system comprising an amphipathic copolymer, and (4) a cleaning agent comprising fumed silica.
B. Brief Description of the Prior Art
Liquid toner compositions for use in developing latent electrostatic images are well-known in the art. Additionally, liquid toner compositions suitable for use in contact electrostatic transfer processes, as well as liquid toner compositions suitable for use in gap electrostatic transfer processes, are documented in the patent literature. In the contact electrostatic transfer process, a toned image is formed on a suitable photoreceptor after which the toned image is brought into contact with a receiver substrate such as paper. An electrostatic potential opposite in polarity of the toner is applied to the receiver substrate (usually by use of a corona) which causes transfer of the toner from the photoreceptor to the receiver substrate. Some commercial examples of this process are the Ricoh and Savin plain paper liquid copiers.
The gap electrostatic transfer process is generally similar to contact transfer except the receiver substrate does not contact the photoreceptor. Instead, it is physically separated by approximately an 0.5 to 10 mil gap. This gap can be filled with carrier liquid or air. Two different approaches to this process are described by Landa (U.S. Pat. No. 4,378,422) and by Bujese (U.S. Pat. No. 4,786,576). The liquid toner requirements for contact and gap electrostatic transfer are quite similar.
Most of the early liquid toner patent literature relates to toners intended for use in relatively low quality black and white copiers. While many of these disclosures are suitable for their intended purposes, most are clearly unacceptable for use in high quality color imaging.
Many recent patents have issued which describe liquid toners intended for high quality color imaging. Many of these toners can be used in contact and gap electrostatic transfer processes. While most of these later toners are superior to those in the early black and white toners, many problems still remain. Specifically, concerning liquid toners intended for contact or gap electrostatic transfer multicolor imaging processes, there remains a need for toners which possess all of the following properties: